1. Field of the Invention
This invention relates generally to semiconductor processing, and more particularly to semiconductor chip solder bump structures and methods of making the same.
2. Description of the Related Art
Flip-chip mounting schemes have been used for decades to mount semiconductor chips to circuit boards, such as semiconductor chip package substrates. In many conventional flip-chip variants, a plurality of solder joints are established between input/output (I/O) sites of a semiconductor chip and corresponding I/O sites of a circuit board. In one conventional process, a solder bump is metallurgically bonded to a given I/O site or pad of the semiconductor chip and a so-called pre-solder is metallurgically bonded to a corresponding I/O site of the circuit board. Thereafter the solder bump and the pre-solder are brought into proximity and subjected to a heating process that reflows one or both of the solder bump and the pre-solder to establish the requisite solder joint.
In one conventional process, the connection of the solder bump to a particular I/O site of a semiconductor chip entails forming an opening in a top-level dielectric layer of a semiconductor chip proximate the I/O site and thereafter depositing metal to establish an underbump metallization (UBM) structure. The solder bump is then metallurgically bonded to the UBM by reflow. In a conventional process for forming a UBM, a titanium layer is blanket deposited on a passivation structure. Thereafter a copper plating layer is deposited on the titanium layer. A polyimide layer is next patterned on the copper plating layer. The polyimide layer is patterned in a doughnut shape with a central opening. A solder barrier layer is next plated in the opening. The uncovered copper and titanium layers are etched to leave a round metal shape beneath the doughnut polyimide. The doughnut polyimide can subsequently delaminate.
The present invention is directed to overcoming or reducing the effects of one or more of the foregoing disadvantages.